I'm not trying to get into it this much, and I'm not trying to be combative here (I kind of hope I am wrong), but it doesn't help that the only name you give me is from pre Red Scare times, and when I look up the name this is one of the first things I see:

In 1919, Berger was convicted of violating the Espionage Act of 1917 for publicizing his anti-interventionist views and as a result was denied the seat to which he had been twice elected in the House of Representatives...Wisconsin promptly held a special election to fill the vacant seat. On December 19, 1919, they elected Berger a second time, and on January 10, 1920, the House again refused to seat him. The seat remained vacant until January 1921, after his previous electoral opponent, Republican William H. Stafford, once again prevailed over Berger in the 1920 general election.

I really just do not believe electoralism will ever be a potential path to power for contemporary leftists in this country. It may once have been, but that was before 'socialist' was a term that became synonymous with 'Nazi' in the minds of many Americans.

Looking at self described socialists we have now, most of them are under the DNC banner, which makes them inherently beholden to that party, their funding at it's whims (and always with the threat of being primaried if they become too problematic)

I am glad to see more socialists in current Congress then I remembered, that does give a little hope for the future. But surely you understand why I'm not exactly optimistic about electoralism as a path forward

The guy who literally wasn't allowed to hold office nationally because he was a socialist? I don't think that proves your idea that socialists can hold office nationally if we just try hard enough